Thiourea adduction



Jan. 25, 1966 J. H. MAHAR 3,231,489

THIOUREA ADDUCTION Filed May 17,. 1962 NIIIII] HSVH NIIIIG HSVIJ REFRIGERATOR STEAM INVENTOR John H. Muhur HYDROCARBON CHARGE CONTAINING BRANCHED CHAIN PARAFFINS United States Patent 3,231,489 THIOUREA ADDUCTION John H. Mahar, Woodbury, N.J., assignor to Socony Mobil Oil Company, Inc., a corporation of New York Filed May 17, 1962, Ser. No. 195,573 9 Claims. (Cl. 208-308) The present invention relates to the separation of branched chain parafiins from mixtures comprising normal and isoparaflins employing thiourea as the adducting material and furfuryl alcohol (furfurol) as the solvent and/or promoter and, more particularly, to the upgrading of gasoline and of jet fuels through thiourea adduction employing furfuryl alcohol as the solvent and/or promoter.

The separation of branched chain parafiins o-r isoparaffins fro'm mixtures comprising normal and branched chain paraffins by adduction of the isoparaffins with thiourea employing as promoters flIld/lOI solvents the lower aliphatic alcohols, i.e., aliphatic alcohols having not more than four carbon atoms and preferably methanol, has been described in several technical publications and United States Patents. However, the separation of the promotensolvent from the raffinate and from the adduct when using the C to C alcohols requires sophisticated fractionating equipment. This can be readily understood when the boiling points of the C to C isoparafiins and the boiling points of the C to C normal paraffins are compared with the boiling points of the C to C aliphatic alcohols. This comparison is made in Table I.

TABLE I C to C normal 0; to C4 alkanol, C to C3 isoparaffin, B.P., F. parafli B.P., F. B.P., F.

C -82. 2 C59. 0 Csl4(). 5 Cs145. 9 Csl21. 5 Cal-136. 4 C7194. l. Cg173. 0 Cr-197. 5 n-C 207. 0 Cr200. 2 i-C3-180. 2 (31-174. 6 h C1-193. 6 nO;243 9 07-176. 9 sec-C,211. 1 C7186. 9 l-C 226. 4 (37-100. 2 t-C 4180. 7 (Ir-114. 2

However, a simple separation means such as a flash drum would reduce capital costs, maintenance costs, and operating costs. Such a simple fractionation means as a flash drum is only efiicient enough when the boiling points of the materials to -be separated differ by at least 100 degrees Fahrenheit. Not only must the difference between the boiling point of the promoter-solvent and the boiling point of the adducted hydrocarbon and the non-adducted hydrocarbon be at least 100 degrees Fahrenheit but the promoter-solvent must also have the capabilities of the lower aliphatic alcohols to enhance the information of the thiourea-hydrocarbon adduct and be a solvent for thiourea miscible with hydrocarbon mixtures to be resolved. It has now been discovered that furfuryl alcohol often referred to as furfurol has the desired characteristics of a promoter-solvent and the boiling point which requires only a simple fractionator such as a flash drum or splitter for separation of the adducted hydrocarbon from the thiourea and for separation of the nonadducted hydrocarbon from the promoter-solvent. This becomes manifest from a consideration of the boiling ice point of furfurol and the boiling range of the product of the isomeriz-ation of the C -C fraction of straight run naphtha. The C -C fraction of straight run naphtha has a boiling range of to F. The isomate boils within approximately the same range. On the other hand, furfuryl alcohol or furfurol boils at 338 F. Thus a very simple means for fractionating the mixture of nonadducted hydrocarbons and promoter-solvent and for fractionating the decomposed thiourea adduct suffices when furfiuryl alcohol is employed as the promoter-solvent. Furfurol possesses the characteristics of a promotersolvent for thiourea adduction as is manifest from the data presented in Table II.

TABLE II (TV-12) lsomateAluminum chloride isomerizaltion product Octane number (Research3 cc. TEL) 94.2 Mol ratio thiourea furfurol isomate=5 .7 5 .0: 1.0.

Adducting temperature, F 80-90 Washing temperature, F. 80-90 Octane number (Re- Hydrocarbon from: search+3 cc. TEL) First filtrate 90.2 Stripped from particle-form solid adduct 102.6

It will be observed that the octane number of the hydrocarbons separated fnom the thiourea adduct was 8.5 oc tane units higher than that of the isomate. Therefore, there can be no question that furfurol is a promoter in the adduction of isoparaffins with thiourea.

Illustrative of the upgrading of isomate are the following examples. Example I A mixture of equal parts of isomate and C to 170 F. fraction of straight run naphtha (said isomate being the product of the isomerization of n-hexane using aluminum chloride as a catalyst) to provide 2,432.6 parts by weight of said mixture, i.e., 519.6 parts by weight (6.6 mols) of hydrocarbon, 1,113 parts by weight of furfuryl alcohol (11.3 mols) and 800 parts by weight of thiourea (10.5 mols) were mixed and held at an adduct formation temperature of about 84 F. for one hour. The mixture was filtered to yield a first filtrate of 1,093 parts by weight. The adduct crystals were washed twice with fresh furfuryl alcohol totaling 1,455 parts by weight (about 15 mols).

The washed particle-form solid adduct was mixed with 1,114 parts by weight (about 11.3 mols) of fresh furfuryl alcohol. The mixture of washed particle-form solid adduct and furfuryl alcohol was heated to a maximum still temperature of 300 F. and a maximum overhead temperature of 138 F. The hydrocarbons recovered from the washed particle-form solid adduct was 108.1 parts by weight. The first filtrate was heated to a maximum overhead temperature of 196 degrees F. and 293.6 parts by weight of hydrocarbons recovered. The Wash filtrate was heated to a maximum overhead temperature of 205 degrees F. and 65.5 parts by weight of hydrocarbons recovered.

The mixture of isomate and naphtha had an octane rating R+3 cc. TEL) of 91.6. The hydrocarbon recovered from the adduct had an octane rating of (R+3 cc. TEL) of 101.0. In other words, the mixture of isomate and C to 170 degrees F. straight run naphtha was upgraded about 10 octane numbers. The hydrocarbon from the first filtrate had an octane rating of 86.5 (R+3 cc. TEL). Thus it is manifest the furfuryl alcohol, sometimes designated furfurol is very effective in the thiourea-adduct separation of isoparafiins from n-paraffins.

The charge mixture, the hydrocarbons from the adduct, and the hydrocarbons from the first filtrate were analyzed 3 by the Mass Spectograph method with the following results:

TABLE HI Hydro- Hydro- Charge carbons carbons Component Mixture, from adduct, from first weight weight filtrate,

(percent) (percent) welght (percent) i-Butane 0. 34 0. 25 O. 34 6. 40 6. 07 7. 31 10. 61 31. 46 5. 09 10. 33 2. 78 24. 46 10. 29 31. 22 12. 48 6. 56 15. 53

Total 49. 38 64. 96 57. 18

1. 59 0. 6O 1. 86 10. 59 3. 14 12. 27 16. 57 4. 40 22. 19 Heptanes 1. 73 1.08 1.18

Total 30. 48 9. 22 37. 50

Oyclopentane 1. 37 2. 98 0. 09 Cyclohexane 1. 81 8.31 0. 18 Methylcyclopentanm 6. 03 13. 58 3. 85

Total. 9. 21 24. S7 4. 12 Benzene 0. 85 0. 94 0. 62 Pentenes 0. 1O 0. 40

The same products as well as the hydrocarbons recovered from the wash filtrate were analyzed by Gas Partition Chromatography with the results set forth in Table IV.

TABLE IV Hydro- Hydro- Hydro- Charge carbons carbons carbons Component Mixture, from from from weight adduct, first wash (percent) weight filtrate, filtrate (percent) weight weight (percent) (percent) i-Butano 0. 74 O. 60 0. 44 0. 39 i-Pentanc 3.83 8. 85 7. 18 7. 63 2,2-dimethylbutane- 12. 74 34. 59 6. 65 12. 33 2,3-dimethylbutano- 5. 85 9. 47 3. 38 4. 87 2-methyl pentane 21. 7 11. 67 24. 85 18. 73 B-methyl pentane 12. 74 7. 11 12.50 12.86

TotaL- 57. 62 72. 29 55. 56.81

n-Butane 2.00 1. 07 2. 2'8 1. 4o n-Pentane 11.93 5. 15 13. 93 12. 57 n-Hexane. 16. 79 4. 81 23. 00 18. 23 Heptanes 0. 51 0. 0. 69 0. 20

Total 31. 23 11. 08 39. 90 32. 49

Cyclopentane 3. 09 3. 00 1. 31 1. 96 Cyclohexane 2. 83 5. 18 0. 28 2. 25 Methylcylcopentane 5. 09 8. 44 3. 35 6. 28

Total 11. 01 16. 62 4. 94 10. 49 Pentenos 0. 0. 10

From the foregoing analyzes and from the octane ratings set forth hereinbefore it is manifest that the components of the charge mixture having the higher octane ratings, i.e., the branched chain parafiins and the cyclic hydrocarbons enriched the hydrocarbons recovered from the adduct.

Example II (TV 14) Thiourea, furfuryl alcohol, and .adductable hydrocarbons were mixed in the mol ratio of 4:4:1 and agitated for about one hour at ambient temperature (80 to 90 F.). The products and the octane ratings (Research '.+3 cc. TEL) thereof are set forth in Table V.

TABLE V Product: Octane Rating (R+3 cc. TEL) Charge Mixture 91.6 Adductcd Hydrocarbons 97.7 Hydrocarbons from First Filtrate 89.3

Hydrocarbons from Wash Filtrate 91.5

Those skilled in the art will recognize that separation of branched chain parafiins by adduction with thiourea in the presence of furfuryl alchol can be used to separate normal paraffins having at least four carbon atoms from branched chain parafiins having four or more carbon atoms in the chain. Thus, a middle distillate, for example kerosine comprising normal paraflins, isoparaffins, cycloparaffins and aromatics having a luminometer number of about 70 can be converted into jet fuel having a luminometer rating of at least 100 by reforming the kerosine in the presence of a reforming catalyst comprising platinum group metal on alumina support to convert substantially all of the cycloparafiins to aromatics. and heavier reformate is contacted with molecular sieve material having pores of about 4 to 5 Angstroms diameter to produce a sieve eflluent comprising isoparaflins, and cyclic hydrocarbons and a sorbate comprising normal paraffins. The efiluent is treated with thiourea and furfuryl alcohol to the form a thiourea adduct, comprising the isoparafiin and thiourea. The adduct is washed with furfuryl alcohol. The washed adduct is then decomposed to yield isoparafiins and thiourea dissolved in furfuryl alcohol. The separated isoparaffins are blended with the n-parafiin sieve sorbate to provide an improved jet fuel having a luminometer number of at least 100 and a lower pour point than the unblended sieve sorbate nparafiins.

Alternatively, the sieve effluent can be extracted with a selective solvent such as sulfur dioxide, di-chlorodiethyl ether and the like having a greater affinity for more aromatic hydrocarbons than for more paraffinic hydrocarbons to obtain an aromatic extract comprising selective solvent and aromatic hydrocarbons and a raffinate comprising iso-parafiins and solvent. The isoparaflins are separated by distillation from solvent and the separated isoparaffins blended with the sieve sorbate n-parafiins to provide a blended jet fuel having a luminometer number of at least 100 and a lower pour point than the unblended sieve sorbate. The aromatic hydrocarbons are recovered in either alternative method of separation for conversion to aromatic hydrocarbons boiling in the gasoline range (dealkylation) or for use per se as aromatic hydrocarbons.

Illustrative of the present method of separating isoparaflins from n-parafiins is the flow of liquids and adduct slurry provided by the flow sheet of the drawing. The flow sheet of the drawing illustrates the separation of the high octane components from the low octane components of an isomate produced by the isomerization of nparaffins in the .presence of aluminum chloride. It will be observed that only a flash drum is required to fractionate or separate the promoter-solvent from the non-adducted hydrocarbons and that the adduct can be decomposed and the adducted hydrocarbons separated from the thiourea dissolved or suspended in furfurol in a very simple fractionating apparatus, to wit: a flash drum or equivalent.

The maximum temperature for adduction and adduct washing is in general, the maximum temperature of the adductable hydrocarbons, i.e., isoparafiins. The minimum temperature for adduction and adduct washing is the freezing point of furfuryl alcohol, i.e., plus 5 F. The prefered temperature for adduct formation and washing of the adduct particles to separate the higher octane components from the lower octane components of a mixture of hydrocarbons boiling in the gasoline range, i.e., isomate, naphtha reformate, naphtha raflinate and the like is in the range of about 40 to about 100 F.

In accordance with the principles of the present invention a solution of thiourea in furfuryl alcohol or a slurry of crystals of thiourea in furfuryl alcohol or a supersaturated solution of thiourea in furfuryl alcohol is prepared in tank 5 in any suitable manner. Thus, thiourea particles are introduced into tank 5 in any suitable manner as by means of hopper 4. Furfuryl alcohol is pumped by a pump (not shown) from a source (notshown) through pipe 6 into tank 5. The particles of thiourea dissolve at least in part in the furfuryl alcohol to provide a solution of thiourea or a slurry of thiourea in furfuryl alcohol in tank 5. Preferably the temperature in tank 5 is in the range of about 50 F. to about 150 F. The solution or slurry of thiourea in furfuryl alcohol flows from tank 5 through pipe 7 to the suction side of pump 8. A start-up the thiourea solution or slurry is pumped by pump 8 through pipes 9 and 65 under control of valve 66 to pipe 56 and thence to coil 57 in means for cooling 3. Presently preferred for cooling the reactant is the well known steam jet refrigerator. After start-up valve 66 is closed and a make-up quantity of thiourea furfuryl solution or slurry is pumped by pump 8 through pipes 9 and 10 to pipe 13.

In cooler or refrigerator 3 the reactant i.e., charge stock hydrocarbon mixture comprising iso-paraflins and nparafiins, e.g., isomate or isomate and C to 170 degrees F. fraction of straight run gasoline is cooled to a temperature at which thiourea forms an adduct with isoparafiins. Thus, for example, the reactants are cooled to at least 100 degrees F., preferably to a temperature in the range of about 40 degrees to about 100 degrees F., or even as low as about 6 degrees to about 10 degrees F.

The charge stock comprising isoparalfins and normal paraffins or molecular sieve effluent, or selective solvent rafiinate, e.g., a mixture of isomate (C and C to 170 degrees F. naphtha flows from a source not shown through pipe 1 to coil 2 in cooler or refrigerator 3.

After start-up, first filtrate, obtained as hereinafter described, flowing from pump 59 through pipe 61 to coil 62 comprising furfuryl alcohol and traces of charge stock is cooled in coil 62 to the adduct formation temperature.

After start-up raflinate residue (obtained as described hereinafter) comprising furfuryl alcohol, thiourea, and traces of isoparafiins flows from pump 54 through pipes 55 and 56 to coil 57. In coil 57 the raflinate residue is cooled to adduct formation temperature.

The charge stock to adduct formation temperature, i.e., maximum temperature below the boiling point of highest boiling adductable hydrocarbon, preferably not higher than about 100 degrees F., minimum temperature about 6 degrees to about 10 degrees F., preferred minimum temperature about 40 degrees F., flows from coil 2 through pipe 12 to reactor 11. The first filtrate cooled to adduct formation temperature in coil 62 flows therefrom through pipe 14 to pipe 17 for use as wash liquid. Raflinate residue cooled in coil 57 to adduct formation temperature flows through pipe 13 in part to reactor 11 and in part through pipe 17 under control of valve 18 to conveyor 16 for use as Wash liquid in washing the adduct particles to remove adhering charge stock as completely as practicable.

It is to be noted that the flow of reactants through coils in cooler or refrigerator 3 is controlled so that while the temperature of each reactant, i.e., charge stock, first filtrate and raffinate residue, is in the range of adduct formature temperature the temperatures of the reactants can be different. The controlling temperature is the temperature of the mixture of charge hydrocarbons, furfuryl alcohol and thiourea in reactor 11. The temperature in reactor 11 is an adduct formation temperature less than the boiling point of the highest boiling adductable hydrocarbon, preferably not higher than 100 degrees F., and not below about 6 degrees F.

The charge mixture, the first filtrate, the raffinate residue and the make-up furfuryl alcohol-thiourea solution or slurry and wash filtrate flowing respectively from pumps 8 and 20 through pipe 10 to pipe 13 enter reactor 11 in proportion to provide a thiourea to furfuryl alcohol to charge mixture mol ratio in the range of 1:1:1 to :25: 1 preferably in the range of 3:3:1 to 15:15:1 and at a temperature in the adduct formation temperature range set forth hereinbefore.

The adductable hydrocarbons of the charge mixture, i.e., the isoparaflins form with the thiourea a particle form solid adduct at the adduct formation temperature. The reaction mixture including the particle form solid adduct flows from reactor 11 through pipe or trough or chute 15 to means for separating the particle form solid adduct from the reaction mixture. Means for separating the adduct particles from the reaction mixture include filter presses, Dorr classifiers and the illustrated conveyor comprising a membrane permeable to furfuryl alcohol and hydrocarbon mounted for movement of the adduct particles from chute or pipe 15 to apron or chute 21 whilst liquid reaction mixture drains from the adduct particles to conduit 38 and wash liquid drains through conduit 19. Thus, the conveyor belt 16 can be flexible continuous foraminous belt moved in any suitable manner as by a motor driven drum 67. The reaction mixture and adduct particles suspended therein flows from pipe or chute 15 onto a belt 16. The liquid reaction mixture drains through the belt into pipe 38. (The liquid reaction mixture which drains through the belt 16 to flow through conduit 38 is designated first filtrate hereinafter.) The first filtrate comprising furfuryl alcohol, non-adducted hydrocarbons, and non-adducted thiourea flows through conduit 38 to the suction side of pump 39. Pump 39 discharges th first filtrate into pipe 40. The first filtrate flows through pipe 40 to indirect heat exchanger 41. In indirect heat exchanger 41 the first filtrate is in heat transfer relation with raflinate residue flowing from flash drum 32. From indirect heat exchanger 41 the first filtrate flows through pipe 42 to indirect heat exchanger 43. In indirect heat exchanger 43 the heated first filtrate is in heat transfer relation with the bottoms of flash drum 47. From indirect heat exchanger 43 the first filtrate flows through pipe 44 to indirect heat exchanger 45. In the indirect heat exchanger 45 the first filtrate is heated in any suitable manner as by steam to a temperature at which the normal paratfins of the charge mixture are separated from 'furfuryl alcohol by vaporization. As illustrated the n-parafiins have lower boiling points than furfurol, i.e., the n-paraffins boil below about 180 degrees P. On the other hand, in the event that the n-paraffins boil above the boiling point of furfuryl alcohol, i.e., above 338 degrees F. the first filtrate is heated to a temperature at which funfury l alcohol is vaporized at atmospheric or sub-atmospheric pressure.

The heated first filtrate flows from indirect heat exchanger 45 through pipe 46 to flash drum or spliter 47. In flash drum or splitcr 47 the n-parafilns of the charge mixture are taken as an overhead through .pipe 48. The n-paraffin overhead flows through conduit 48 to cooler 49. In cooler 49 the n-paraffin overhead is cooled to a temperature at which the most volatile n-paraflins of the charge mixture is condensed. The condensed nwparaflins flow from cooler 49 through pipe 50 to the suction side of pump 51. Pump 51 discharges the n-paraflins into pipe 52 through which the n-paraflins flow to storage, blending, distribution and the like.

Returning now to means 68 for separating adduct particles from liquid reaction mixture and wash liquid; the adduct particles on belt 16 pass the point at which the preponderant portion of the liquid reaction mixture has drained from the adduct particles to drain 38. Thereafter the adduct particles are washed with ralfinate residue flowing from coil 57 through pipes 13 and 17 under control of valve 18 at an adduct formation temperature in the range set forth hereinbefore, i.e., at a temperature not in excess of degrees F. The raffinate residue, comprising thiourea from the adduct particles and furfuryl alcohol, flows from pipe 17 over the adduct particles on the foraminous continuous belt 16 and Washes adhering or adduct entrained reaction mixture, primarily nonadducted hydrocarbons, from the adduct particles. The wash liquid and adduct particle washings, designated wash filtrate hereinafter, flows through conduit 19 to the suction side of pump 20. Pump 20 discharges the wash filtrate into pipe 69. The wash filtrate comprising furfuryl. alcohol and non-adducted hydrocarbons of the charge mixture flows through pipe 69 to pipe 10. In pipe the wash filtrate is mixed with make-up furfuryl alcohol-thiourea solution or slurry flowing from pipe 9. The mixed wash filtrate and make-up furfuryl alcoholthiourea solution or slurry flows through pipe 10 to pipe 13 and thence to reactor 11.

is in heat transfer relation with the first filtrate. From indirect heat exchanger 41 the raflinate residue flows through pipe 56 to coil 57 in refrigerator 3..

Illustrative of the separation of higher octane rating hydrocarbons from lower octane rating hydrocarbons of aluminum chloride isomate are the data presented in Table VI.

Wash solvent, furfuryl alcohol: Volume of solvent each wash 2 Number of washes Adduct decompositio l Solvent volume furfuryl alcohol 1 1. 4 l. 1 1. 25 1. 25 2. 8

Maximum solvent stripping temp. F 220 298 300 189 215 155 155 Recovered high octane hydrocarbons, percent by weight 37. 5 34. 2 23. 2 6. 7 24. 7 39. 5 Maximum octane No.

increase 5. 5 8. 4 9. 4 5. 2 6. 0 4. 6

1 Ca isomate (A101 Catalyst), 2 Based on hydrocarbon charge. BStil1. T-Overhead.

The adduct particles deposited on belt 16 are discharged onto apron or chute 21 down which the adduct particles flow to tank 22 provided with an agitator 23 driven by electric motor 24 or any other suitable means. Tank 22 is also provided with inlet means for introducing furfuryl alcohol or bottoms from flash drum 47 into tank 22.

The adduct particles and added furfuryl alcohol or flash drum bottoms flow from tank 22 through pipe 25 to the suction side of pump 26. Pump 26 discharges the adduct and furfuryl alcohol into pipe 27, through which the mixture flows to means for decomposing the adduct into adducted hydrocarbons and thiourea. (The amount of furfuryl alcohol introduced into tank 22 is at least suificient to provide a solution of thiourea in fur-.

furyl alcohol at the temperature in votator or decomposer 28, i.e., at a temperature below 300 degrees F.)

In votator or decomposer 28 the mixture of adduct and furfuryl alcohol, i.e., first filtrate bottoms of flash drum or splitter 47, is heated in any suitable manner as by an immersed steam coil into which steam flows through pipe 29 and from which steam flows through pipe 30 to a temperature above 100 degrees F. and below 300 de grees F. e.g., a temperature in the range of about 150 degrees to about 280 degrees F. at Which the adduct is decomposed into adducted hydrocarbons, i.e., isoparaffins and adduct, i.e., thiourea. The mixture of furfuryl alcohol, thiourea, and isoparaffins flows from votator 28 through pipe 31 to flash drum or splitter 32.

In flash drum or splitter 32 the adducted hydrocarbons are taken overhead through pipe 33. The adducted hydrocarbons flow through pipe 33 to cooler 34. In cooler 34 the adducted hydrocarbons are cooled to a temperature at which the lowest boiling adducted hydrocarbon is liquid. The cooled adducted hydrocarbons flow from the cooler 34 through pipe 35 to the suction side of pump 36. Pump 36 discharges the adducted hydrocarbons into pipe 37 through which the adducted hydrocarbons flow to storage, blending, distribution, etc.

The bottoms of flash drum or splitter 32, designated raflinate residue, flow therefrom through pipe 53 to the suctionside of pump 54. Pump 54 discharges the raffinate .residue into pipe 55. The raflinate residue comprising furfuryl alcohol and thiourea (from the adduct particles) flows through pipe 55 to indirect heat exchanger 41. In heat exchanger 41 the raflinate residue A tabulation of the total volume of furfuryl alcohol used to wash the adduct particles, the weight percent yield of high octane components recovered, and the increase in octane rating provides interesting information.

TABLE VII Run Total Weight A Octane Vol. hydro- No. volume of percent No. (RXA) Carbons wash recovered From the foregoing tabulations, Table VI' and VII, it is manifest that the total volume of wash liquid, i.e., furfuryl alcohol, based upon the volume of charge hydrocarbons preferably is in the range of 0.6 to 1.6.

I claim:

1. A method of separating branched chain paraffins from straight chain paraflins which comprises mixing (1) a charge hydrocarbon mixture comprising branched chain paraflins and straight chain parafiins, (2) thiourea, and (3) furfuryl alcohol to provide a molal ratio of thiourea: furfuryl alcohol: charge hydrocarbon mixture in the range of 1:1:1 to 25:25:1, holding the mixture so formed at an adduct formation temperature not exceeding the boiling point of the lowest boiling component of said hydrocarbon mixture and above the freezing point of furfuryl alcohol to produce a particle-form solid adduct comprising thiourea and branched chain paraflins, separating said particle-form solid adduct from liquid reaction mixture, washing said particle-form solid adduct with wash liquid comprising furfuryl alcohol to obtain washed particle-form solid adduct having a reduced content of non-adducted hydrocarbons, admixing furfuryl alcohol with said washed particle-form solid adduct to obtain a mixture for decomposing said addzuct consisting essentially of particle-form solid adduct and furfuryl alcohol, heating said mixture of said particleforrn solid adduct and said furfuryl alcohol at a temperature below about 300 F. to decompose said particle-. form solid adduct and to produce a mixture comprising furfuryl alcohol branched chain paraflins per se and thiourea per se, separating branched chain paraflins from said mixture at a temperature below about 300 F. and above an adduct formation temperature, and recovering said branched chain parafiins.

2. The method of separating branched chain parafiins from straight chain paraffins as set forth in claim 1, wherein the charge hydrocarbon mixture comprises an isomate of C hydrocarbons,

3. The method of separating branched chain paratfins from straight chain parafiins as set forth in claim 1 wherein the charge hydrocarbon mixture comprises a reformate.

4. The method of separating branched chain parafiins from straight chain paraflins as set forth in claim 1 wherein the charge hydrocarbons mixture comprises the effluent produced when contacting the reformate of a fuel fraction of petroleum boiling above 200 F. with molecular sieve material having 4 to 5 angstrom diameter pores.

5. The method of separating branched chain parafiins from straight chain paraifins as set forth in claim 1 wherein the adduct formation temperature is below 100 F.

6. The method of separating branched chain paraflins from straight chain parafiins as set forth in claim 1 wherein the molal ratio of thiourea: furfuryl alcohol: charge hydrocarbon mixture is in the range of 3:3:1 to :15:1.

7. The method of separating branched chain paraffins from straight chain paraflins as set forth in claim 1 wherein the charge hydrocarbon mixture comprises the isomate of C and C parafiins and wherein the adduct formation temperature is in the range of about 40 to about 100 F.

8. The method of separating branched chain paraifins from straight chain parafiins as set forth in claim I wherein normal parafiins are separated from the liquid reaction mixture.

9. The method of separating branched chain parafiins from straight chain paraffins as set forth in claim 1 wherein normal paraflins are separated from the liquid reaction mixture to provide normal product and first filtrate comprising fur'furyl alcohol and thiourea, and wherein (1) fiurfuryl alcohol and thiourea obtained in the decomposition of particle-form solid adduct, designated rafiinate residue, (2) the washings from washing the particle-form adduct at least in part, and (3) the aforesaid first filtrate are recycled to the adduct formation stage.

References Cited by the Examiner UNITED STATES PATENTS 2,637,681 5/1953 Arnold et al. 26096.5 X 2,642,378 6/1953 Barnes et al. 26096.5 X 2,642,424 6/ 1953 Gorin et al. 26096.5 2,653,122 9/1953 Arnold et al. 260965 X 2,899,377 8/1959 Findlay 20862 2,914,455 11/1959 Keller 20825 2,917,447 12/1959 Hoppe et al. 208-25 2,944,001 7/1960 Kirnberlin et al. 260676 2,958,644 11/ 1960 Kimberlin et al. 260676 2,981,675 4/1961 Hemminger et al. 2089S 2,983,668 5/1961 Hemminger 208 3,001,927 9/1961 Gerhold et a1. 260676 DELBERT E. GANTZ, Primary Examiner.

MILTON STERMAN, ALPHONSO D. SULLIVAN, Examiners. 

1. A METHOD OF SEPARATING BRANCHED CHAIN PARAFFINS FROM STRAIGHT CHAIN PARAFFINS WHICH COMPRISES MIXING (1) A CHARGE HYDROCARBON MIXTURE COMPRISING BRANCHED CHAIN PARAFFINS AND STRAIGHT CHAIN PARAFFINS, (2) THIOUREA, AND (3) FURFURYL ALCOHOL TO PROVIDE A MOLAL RATIO OF THIOUREA: FURFURYL ALCOHOL: CHARGE HYDROCARBON MIXTURE IN THE RANGE OF 1:1:1 TO 25:25:1, HOLDING THE MIXTURE SO FORMED AT AN ADDUCT FORMATION TEMPERATURE NOT EXCEEDING THE BOILING POINT OF THE LOWEST BOILING COMPONENT OF SAID HYDROCARBON MIXTURE AND ABOVE THE FREEZING POINT OF FURFURYL ALCOHOL TO PRODUCE A PARTICLE-FORM SOLID ADDUCT COMPRISING THIOUREA AND BRANCHED CHAIN PARAFFINS, SEPARATING SAID PARTICLE-FORM SOLID ADDUCT FROM LIQUID REACTION MIXTURE, WASHING SAID PARTICLE-FORM SOLID ADDUCT WITH WASH LIQUID COMPRISING FURFURYL ALCOHOL TO OBTAIN WASHED PARTICLE-FORM SOLID ADDUCT HAVING A REDUCED CONTENT OF NON-ADDUCTED HYDROCARBONS, ADMIXING FURFURYL ALCOHOL WITH SAID WASHED PARTICLE-FORM SOLID ADDUCT TO OBTAIN A MIXTURE FOR DECOMPOSING SAID ADDUCT CONSISTING ESSENTIALLY OF PARTICLE-FORM SOLID ADDUCT AND FURFURYL ALCOHOL, HEATING SAID MIXTURE OF SAID PARTICLEFORM SOLID ADDUCT AND SAID FURFURYL ALCOHOL AT A TEMPERATURE BELOW ABOUT 300*F. TO DECOMPOSE SAID PARTICLEFORM SOLID ADDUCT AND TO PRODUCE A MIXTURE COMPRISING FURFURYL ALCOHOL BRANCHED CHAIN PARAFFINS PER SE AND THIOUREA PER SE, SEPARATING BRANCHED CHAIN PARAFFINS FROM SAID MIXTURE AT A TEMPERATURE BELOW ABOUT 300*F. AND ABOVE AN ADDUCT FORMATION TEMPERATURE, AND RECOVERING SAID BRANCHED CHAIN PARAFFINS. 